At this specific stage in development, I agree that the phrase "pay to win" can be accurately applied in the objective sense. You can buy ships with real money and some of those ships are going to be better than others in a dogfight. As others have said, Roberts is promising that the ship purchase system will only use in-game currency once the game actually comes out but until that happens, it is hard to really argue against the "pay to win" accusation.
That being said, there is another angle here that is worth at least considering. Before I go on, I need to make sure that I offer a disclaimer here. I bought into Star Citizen but only with the $35 entry level ship. I have been a backer for quite some time but not really a active one by any real measure. I read the newsletters that come in my email and occasionally take a look at some reddit discussions about it but I don't really call myself a "fan" at this stage as I am just kinda waiting for something that resembles the final product.
With that disclaimer out of the way. Star Citizen's way of handling ships complicates the "pay to win" statement. Unlike a game like EVE or even Elite Dangerous, Star Citizen is skewing slightly (but not entirely) towards the "sim" part of space combat sim. It does this not in terms of the accuracy of its physics or the realism of the ships and their systems/weapons but instead in the specific roles that a ship fills.
When you look at the line-up of ships and how they work, you will start to see that this is not the kind of game where a single player can buy a big, expensive ship and start wrecking everything around them. Larger ships are going to skew more towards deploying smaller ships (piloted by players) and even larger, anti-capital ship weapons.
As you step down to the mid-sized ships, you see that many are focused more on cargo and can't really expect to survive in a one on one against even a fighter.
The fighters are where the real combat potential for your average player will come into play. Unlike the larger ships, the fighters will be cheaper to support, easy to operate with a single player, and will be fast and nimble enough to give most things a really, really hard time.
Specialization is the key here. Players who are buying huge ships right now are going to be in for a shock when they find that outside of specific situations, they are not going to be practical and will probably be more of a liability than a asset. Likewise, those who invest heavily in mid-sized ships will need to come to terms with the fact that they are not in fighters and will probably be easy meat for anyone in even the entry level (cheap) ships.
Still, to be fair. Some of those fighters do fall into the "pay to win" category right now. A person who buys one of those $100 fighters is probably going to have a easier time blowing up other ships but at the same time, they won't be able to do much else unless they have something else in their hanger.
So, yeah. "pay to win" is certainly a factor here but if things go as CIG states they will on release, it becomes not so much a greed thing but more of a unfortunate byproduct of how the early access program works and what the final game is supposed to be like. CIG is shooting for a wide selection of very specialized ships and some of them are going to be better at combat than others. Since they are using the money from ship purchases to make the game, it is only natural that you end up with a "pay to win" situation until the real money part is removed from the ship purchase process. It is just the nature of the kind of ships this game will have.
This is not a attempt at convincing you to get into it or anything. I have no stake in what you do or do not do with your free time. I just wanted to give you my perspective on this as it seems that people do rather quickly apply the "pay to win" thing even when it is a bit more complicated.
This is something that I deal with a lot with a combat sim I play called DCS World. People see the individual aircraft modules you can purchase and assume that means it is "pay to win" but in DCS World, each of the aircraft serve specific purposes and it falls on the mission designers to put the aircraft into their proper context in order for them to succeed. Still, on the surface, it does look like "pay to win" so people get stuck on that really quickly and don't tend to budge from it easily.